Penbutolol Sulfate

Trade Names:Levatol- Tablets 20 mg

Pharmacology

Nonselectively blocks beta-adrenergic receptors, primarily affecting the CV system (eg, decreased heart rate, decreased cardiac contractility, decreased BP) and lungs (promotes bronchospasm).

Pharmacokinetics

Absorption

Absorption is rapid and complete (100%). The t _max is 2 to 3 h.

Distribution

Protein binding is 80% to 98%. Penbutolol crosses the placenta.

Metabolism

Hepatic metabolism is by conjugation and oxidation.

Elimination

Urine (90% excreted in urine, 1/ 6 as penbutolol conjugate). Penbutolol plasma t _½ is approximately 5 h; conjugated penbutolol is approximately 20 h, 25 h in elderly patients, and approximately 100 h in patients on renal dialysis.

Special Populations

Accumulation of penbutolol conjugates may be expected.

Indications and Usage

Management of mild to moderate hypertension.

Contraindications

Greater than first-degree heart block; CHF unless secondary to tachyarrhythmia or untreated hypertension treatable with beta-blockers; overt cardiac failure; sinus bradycardia; cardiogenic shock; hypersensitivity to beta-blockers; untreated bronchial asthma or bronchospasm, including severe COPD.

Dosage and Administration

PO 20 mg every day.

General Advice

Administer without regard to meals. Administer with food if GI upset occurs.

Storage/Stability

Store tablets at controlled room temperature (59° to 86°F). Protect from light.

Drug Interactions

May attenuate or reverse antihypertensive effect; potentially life-threatening increases in BP, especially on withdrawal.

Initial hypertensive episodes followed by bradycardia may occur.

Peripheral ischemia, manifested by cold extremities and possible gangrene.

Prolonged hypoglycemia with masking of symptoms.

Increased lidocaine levels, leading to toxicity.

Some agents may impair antihypertensive effects.

Elimination of theophylline may be reduced; effects of both drugs may be reduced by pharmacologic antagonism.

Effects of both drugs may be increased.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Bradycardia; hypotension; CHF; edema; worsening angina, atrioventricular (AV) block.

CNS

Dizziness; tiredness; fatigue; headache; insomnia; depression; short-term memory loss; emotional lability.

Dermatologic

Sweating.

EENT

Dry eyes; visual disturbances.

GI

Diarrhea; nausea; dyspepsia.

Genitourinary

Impotence.

Hematologic

Agranulocytosis; nonthrombocytopenic and thrombocytopenic purpura.

Metabolic

May increase or decrease blood sugar.

Respiratory

Cough; dyspnea; bronchospasm.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy not established.

CHF

Administer cautiously in CHF patients controlled by digitalis and diuretics.

Diabetics

May mask signs and symptoms of hypoglycemia (eg, tachycardia, BP changes). May potentiate insulin-induced hypoglycemia.

Nonallergic bronchospasm

Give drug with caution to patients with bronchospastic disease.

Thyrotoxicosis

May mask clinical signs of developing or continuing hyperthyroidism (eg, tachycardia). Abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm.

Abrupt withdrawal

A beta-blocker withdrawal syndrome (eg, hypertension, tachycardia, anxiety, angina, MI) may occur 1 to 2 wk after sudden discontinuation of systemic beta-blockers. If possible, gradually withdraw therapy over 1 to 2 wk.

Anaphylaxis

May be unresponsive to usual doses of epinephrine; aggressive therapy may be required.

Peripheral vascular disease

May precipitate or aggravate symptoms of arterial insufficiency.

Overdosage

Symptoms

Bradycardia, hypotension, CHF, AV block, intraventricular conduction defects, asystole, coma.

Patient Information

• Warn patient to never stop taking this medication suddenly. Rebound effects can produce angina, and even MI. Explain that medication will be tapered slowly before discontinuation.
• Instruct patient to take medication at the same time every day.
• Advise patient not to take any OTC medications such as nasal decongestants, diet aids, cold preparations, or antihistamines without consulting the health care provider first.
• Teach patient and family how to take pulse. Instruct them to check it before taking the medication. If the pulse is irregular or has a rate less than 60 bpm, notify health care provider before taking the medication.
• Instruct patient and family on how to take BP. If BP is markedly lower than normal, notify health care provider.
• Warn patient that sudden position changes may cause dizziness caused by postural hypotension.
• Instruct patient to notify health care provider if any of the following occur: confusion, depression, memory loss, rash, shortness of breath, slowed pulse rate, or unusual bruising or bleeding.

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